Resistance generating device for drive unit

ABSTRACT

A resistance generating device for a drive unit of an opening and closing member of a vehicle includes a transmission member transmitting a rotary motion to a rotary body, and a fixing member provided to form a clearance between the fixing member and the transmission member in a radial direction of a rotary axis of the transmission member. One of the fixing member and the transmission member includes a magnet and the other includes a magnetic body. The magnet is disposed to face the magnetic body so that the facing position facing each other is changed as the transmission member rotates. The magnet is disposed to face the magnetic body so that magnetic poles at the facing position alternate as the transmission member rotates. The magnetic body and the magnet generate a magnetic force therebetween, the magnetic force generating a resistance against an opening and closing movement of the opening and closing member.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is based on and claims priority under 35 U.S.C. §119 toJapanese Patent Application 2014-017518, filed on Jan. 31, 2014, theentire content of which is incorporated herein by reference.

TECHNICAL FIELD

This disclosure generally relates to a resistance generating device fora drive unit which opens and closes an opening and closing member of avehicle.

BACKGROUND DISCUSSION

A known vehicle is provided with a drive unit that opens and closes anopening and closing member, for example, a back door (i.e., serving asan opening and closing member), a swing door, a slide door, and awindow. For example, a first end portion of the drive unit that opensand closes the back door (tailgate) includes a coupling connected to avehicle body, and a second end portion of the drive unit includes acoupling connected to the opening and closing member. The drive unitincludes a threaded spindle, a spindle nut and a spindle tube. Thethreaded spindle rotates by motive power of a motor and human power(power) of an operator. The spindle nut is threaded with the threadedspindle. The spindle tube includes a first end portion which is fixed tothe spindle nut and a second end portion which is fixed to the couplingconnected to the opening and closing member.

In a case where the threaded spindle rotates by motive power, rotarymotion of the threaded spindle is converted into linear motion of thespindle nut by the threaded spindle and the spindle nut. Accordingly,the spindle tube fixed to the spindle nut moves linearly to open andclose the opening and closing member. In addition, the drive unit isconstructed to open and close the opening and closing member manually byan operator.

The drive unit includes a compressive coil spring for holding theopening and closing member in an opened state. The compressive coilspring holds the opening and closing member in the opened state bygenerating reaction force which balances with the weight of the openingand closing member per se. As disclosed in JP4885910B (hereinafterreferred to as Patent reference 1), a drive unit is provided with aresistance generating device which generates resistance against rotarymotion of a threaded spindle in order to hold an opening and closingmember in an opened state even in a case where an external force, forexample wind or snow, is applied to the opening and closing member.

As disclosed in Patent reference 1, the resistance generating device fora drive unit includes the threaded spindle and a spindle nut. Theresistance generating device disclosed in Patent reference 1 is providedwith a fixing member, a ring magnet and a rotary member. The fixingmember is made from non-magnetizable material, for example, plastic oraluminum. The ring magnet is disposed inside the fixing member. Therotary member is placed outside the fixing member. In a case where amotor is in a stopped state, magnetic force of the ring magnet attractsthe rotary member toward the fixing member to have the rotary membercontact the fixing member. Accordingly, resistance against the rotarymotion of the rotary member is generated. On the other hand, in a casewhere the motor is in motion, the centrifugal force is applied to therotary member and releases resistance against the rotary motion of therotary member because the rotary member separates from the fixingmember.

Another resistance generating device for a window, a door, a lid and ashelf of a building material, furniture, vehicle and machinery isdisclosed in JP2005-265174A (hereinafter referred to as Patent reference2). The resistance generating device disclosed in Patent reference 2includes a fixing member and a rotary member. Each of the fixing memberand the rotary member is provided with the north pole magnets and thesouth pole magnets which are alternately disposed with each other. Thefixing member and the rotary member are disposed close to, and facingwith each other. The rotary member rotates relative to the fixing memberin a non-contact manner. The magnetic force generates resistance againstrotary motion of the rotary member.

However, according to Patent reference 1, because resistance isgenerated by frictional force having an unstable characteristic,resistance force may be largely changed due to abrasion deterioration orwetting of a surface of the fixing member or the rotary member and dueto extraneous materials (abrasion powder) attached to the surface of thefixing member or the rotary member. Further, friction noise may begenerated in a case where the rotary member slides relative to thefixing member. Similarly, contact noise (for example, tapping sound) maybe generated in a case where the rotary member comes in contact with thefixing member. In addition, a large number of members may be necessaryto move the rotary member by an application of the centrifugal force,which complicates the construction of the resistance generating device.

According to Patent reference 2, because the rotary member rotatesrelative to the fixing member in a non-contact manner to generateresistance, the abrasion of the surface of the fixing member or therotary member does not occur. However, the resistance generating devicedisclosed in Patent reference 2 costs high because both the rotarymember and the fixing member are provided with magnets.

A need thus exists for a resistance generating device for a drive unitwhich is not susceptible to the drawback mentioned above.

SUMMARY

According to an aspect of this disclosure, a resistance generatingdevice for a drive unit opening and closing an opening and closingmember of a vehicle includes a rotary body being rotated for opening andclosing the opening and closing member, a transmission member beingrotated in response to an applied power, the transmission membertransmitting a rotary motion to the rotary body, and a fixing memberprovided to form a clearance between the fixing member and thetransmission member in a radial direction of a rotary axis of thetransmission member, the fixing member surrounding a periphery of thetransmission member. One of the fixing member and the transmissionmember includes a magnet and the other of the fixing member and thetransmission member includes a magnetic body. The magnet is disposed toface the magnetic body so that a facing position of the magnet and themagnetic body facing each other is changed as the transmission memberrotates. The magnet is disposed to face the magnetic body so thatmagnetic poles at the facing position of the magnet and the magneticbody alternate as the transmission member rotates. The magnetic body andthe magnet generate a magnetic force therebetween, the magnetic forcegenerating a resistance against an opening and closing movement of theopening and closing member.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and additional features and characteristics of thisdisclosure will become more apparent from the following detaileddescription considered with the reference to the accompanying drawings,wherein:

FIG. 1 is a view showing a drive unit mounted to a back door of avehicle according to embodiments disclosed here;

FIG. 2A is a cross sectional view of the drive unit in a case where theback door is fully closed according to the embodiments;

FIG. 2B is a cross sectional view of the drive unit in a case where theback door is fully opened according to the embodiments;

FIG. 3 is a longitudinal cross sectional view of a resistance generatingdevice of a first embodiment;

FIG. 4 is a lateral cross sectional view of the resistance generatingdevice taken along line IV-IV in FIG. 3;

FIG. 5 is a view showing a relationship between a rotary angle of aniron core and power applying to the iron core;

FIG. 6 is a lateral cross sectional view of a resistance generatingdevice according to a second embodiment disclosed here;

FIG. 7 is a lateral cross sectional view of a resistance generatingdevice according to a modified example of the second embodimentdisclosed here;

FIG. 8 is a view showing a relationship between a rotary angle of atransmission member and power applying to the transmission memberaccording to the second embodiment;

FIG. 9 is a lateral cross sectional view of a resistance generatingdevice according to a third embodiment disclosed here;

FIG. 10 is a lateral cross sectional of a resistance generating deviceaccording to a modified example of the third embodiment disclosed here;

FIG. 11 is an exploded perspective view of a resistance generatingdevice of a fourth embodiment disclosed here;

FIG. 12 is a perspective view of a transmission member of the fourthembodiment;

FIG. 13 is a view showing a facing surface of a first transmissionmember which faces a second transmission member according to the fourthembodiment;

FIG. 14 is a view showing a facing surface of the second transmissionmember which faces the first transmission member according to the fourthembodiment;

FIG. 15A is an explanatory view of the transmission member showing aninitial state where the first transmission member and the secondtransmission member are not in a relatively rotated state with eachother according to the fourth embodiment;

FIG. 15B is an explanatory view of the transmission member showing adisplaced state where the first transmission member and the secondtransmission member are in a relatively rotated state with each otheraccording to the fourth embodiment; and

FIG. 16 is a perspective view of the transmission member showing thedisplaced state of the first transmission member and the secondtransmission member in a case where the first transmission member andthe second transmission member relatively rotate with each otheraccording to the fourth embodiment.

DETAILED DESCRIPTION

Embodiments of this disclosure will be explained with reference to thedrawings. For example, sizes, materials, forms and relative positions ofcomponents shown in the embodiments are not limited to the embodimentsunless any specific descriptions are given.

A drive unit is used for opening and closing an opening and closingmember, for example, a swing door, a slide door, and a window of avehicle. According to the embodiments, a magnet-type door holding devicefor a spindle-type powered-back door will be explained as one example ofthe drive unit. Alternatively, the drive unit can be used for raisingand lowering a vehicle seat.

As shown in FIG. 1, a drive unit 100 corresponds to a drive unit for thespindle-type powered-back door. The drive units 100 are disposed atopposing sides of a vehicle body 150A of a vehicle 150 in a widthdirection and are interposed between the vehicle body 150A and a backdoor 200. A first coupling 102 and a second coupling 104 are provided atopposing end portions of the drive unit 100. The first coupling 102 ofthe drive unit 100 is connected to the vehicle body 150A. The secondcoupling 104 of the drive unit 100 is connected to the back door 200(i.e., serving as an opening and closing member), A cylindrical covertube 106 moves relative to a cylindrical-shaped housing tube 107 by amotor 110 built in the drive unit 100 to open and close the back door200.

As shown in FIGS. 2A and 2B, the drive unit 100 includes the housingtube 107 and the cover tube 106 which is fitted to the housing tube 107telescopically. The cover tube 106 can reciprocate in an axial directionrelative to the housing tube 107. The cover tube 106 and the housingtube 107 construct a telescopic tube which is extendable andcontractible. An end portion of the housing tube 107 is provided withthe first coupling 102 and an end portion of the cover tube 106 isprovided with the second coupling 104.

The motor 110 serving as a drive source of the drive unit 100 iscontained in the housing tube 107. A rotary shaft 111 of the motor 110is connected to a reduction gear 112 which corresponds to a planetarygear. The reduction gear 112 is connected to the resistance generatingdevice 1 and transmits motive power of the motor 110 to the resistancegenerating device 1. The resistance generating device 1 is connected toa threaded spindle 113 (i.e., serving as a rotary body) and transmitsthe rotary motion of the motor 110 to the threaded spindle 113.

The spindle nut 114 is threaded onto the threaded spindle 113. Thethreaded spindle 113 is rotatably held or retained by the housing tube107. The threaded spindle 113 is positioned within a cylindrical-shapedspindle tube 115. One end portion of the spindle tube 115 is fixed tothe spindle nut 114 while the other end portion of the spindle tube 115is fixed to the second coupling 104 and the cover tube 106.

A compressive coil spring 116 is contained inside the cover tube 106.The compressive coil spring 116 generates biasing force that balanceswith the weight of the back door 200 per se or that exceeds holdingforce for holding the weight of the back door 200.

In a case where the motor 110 rotates, the threaded spindle 113 rotatesvia the reduction gear 112 and the resistance generating device 1. Thethreaded spindle 113 is threaded onto the spindle nut 114 so that therotary motion of the threaded spindle 113 is converted into linearmotion of the spindle nut 114 and the spindle tube 115. The linearmotion of the spindle nut 114 and the spindle tube 115 moves the covertube 106 relative to the housing tube 107 to open and close the backdoor 200.

In a case where the back door 200 is fully closed, as shown in FIG. 2A,the spindle nut 114 is disposed at a lower portion of the threadedspindle 113. Most portions of the cover tube 106 cover the housing tube107. That is, the telescopic tube is in a contracted state. In a casewhere the motor 110 rotates to open the back door 200, the spindle nut114 moves upward in response to the rotation of the threaded spindle113. In a case where the back door 200 is fully opened, as shown in FIG.2B, the spindle nut 114 is disposed at an upper portion of the threadedspindle 113. The cover tube 106 moves upward relative to the housingtube 107. That is, the telescopic tube is in an extended state.

The cover tube 106 can be stopped at any desirable positions relative tothe housing tube 107. The weight of the back door 200 per se is appliedto the cover tube 106 which is stopped at the desirable position,however, the weight of the back door 200 per se balances with biasingforce applied by the compressive coil spring 116. Thus, the back door200 can be stopped at any desirable positions. In a case where anundesirable external force, for example wind, is applied to the backdoor 200, the resistance generating device 1 generates resistanceagainst the opening and closing motions of the back door 200 andmaintains the position of the back door 200.

The resistance generating device 1 of a first embodiment will beexplained as follows. The drive unit 100 includes the compressive coilspring 116 to inhibit the back door 200 from being closed by the ownweight of the back door 200 in a case where the back door 200 is in anopened state. However, according to a known back door of a vehicle, in acase where a load, for example wind or snow, is applied to the back doorin a state where the back door is in the opened state, the back door maybe closed undesirably. In those circumstances, the drive unit 100 isprovided with the resistance generating device 1 so as not to close theback door 200 even in a case where some degree of the external force isapplied to the opened back door 200.

As shown in FIGS. 3 and 4, the resistance generating device 1 isprovided with a rotatable iron core 2 (i.e., serving as a transmissionmember, a magnetic body) and a ring magnet 3 (i.e., serving as a fixingmember, a magnet) which surrounds an outer circumference of the ironcore 2 in a non-contact manner.

The iron core 2 includes a first connection portion 4 (power receivingportion) disposed at a first end portion 2 a and a second connectionportion 5 disposed at a second end portion 2 b. The first connectionportion 4 is connected to the reduction gear 112. The second connectionportion 5 is connected to the threaded spindle 113. The first connectionportion 4 rotates in response to motive power of the motor 110 via thereduction gear 112. The iron core 2 transmits rotary motion received atthe first connection portion 4 to the threaded spindle 113. According tothe embodiment, the first connection portion 4, the second connectionportion 5 and the iron core 2 are integrally formed. Alternatively, eachof the first connection portion 4 and the second connection portion 5may be formed individually, or separately from the iron core 2. The ironcore 2 includes a magnetic body, that is, a material that is attractedto a magnet (ferromagnetic body). The iron core 2 per se is favorably amagnetic body that does not have magnetic poles, for example, the southmagnetic pole or S pole, or the north magnetic pole or N pole.

The ring magnet 3 includes plural magnetic poles, and the S poles andthe N poles are alternately arranged on the ring magnet 3 in acircumferential direction. According to the embodiments, the ring magnet3 includes, for example, four magnetic poles which are configured by twoS-poles and two N-poles (see FIG. 5), however is not limited.Alternatively, the number of the magnetic poles may be, for example,two, six, and eight. According to the embodiments, the ring magnet 3 isa permanent magnet. Alternatively, the ring magnet 3 can be anelectromagnet as needed.

According to the embodiments, the ring magnet 3 is used, however amagnet does not need to be formed in a ring shape. Alternatively, pluralseparated magnets are applicable. The ring magnet 3 is held by a holder7. The holder 7 is fixed within the housing tube 107 of the drive unit100. Alternatively, the ring magnet 3 may be held directly within thehousing tube 107 without the holder 7.

As shown in FIG. 3, the first and second end portions 2 a, 2 b arerotatably supported by bearings 8, respectively, so that the iron core 2rotates about a rotary axis X. The bearings 8 are held by the holder 7and a holder cap 9. In a case where the rotary axis X of the iron core 2is not precisely coaxial with an axis of the ring magnet 3, the ironcore 2 may come in contact with the ring magnet 3 in response to therotation of the iron core 2. In those circumstances, each of thebearings 8 is attached to the first and second end portions 2 a and 2 bof the icon core 2 in order to secure the accuracy of the positioning ofthe rotary axis X of the iron core 2 relative to the axis of the ringmagnet 3. Accordingly, the iron core 2 securely rotates relative to thering magnet 3 in the non-contact manner.

The bearing 8 favorably corresponds to a sliding bush or a rollingbearing. In a case where the bearings 8 are held by the holder 7, theiron core 2 can rotate stably. Alternatively, the bearings 8 may bedirectly held by the ring magnet 3 instead of the holder 7. The ironcore 2 disposed inside the ring magnet 3 is provided with pluralprotrusions 6 (i.e., serving as a magnetic body, a magnetic bodyportion) which are formed in fan-shaped wings. The whole body of theiron core 2 including the plural protrusions 6 is made from the magneticbody. A surface of the iron core 2 can be coated with a coating materialto inhibit corrosion. Alternatively, a non-magnetic body can cover gapsbetween the plural protrusions 6 so that the iron core 2 can be formedin a substantially cylindrical shape.

According to the first embodiment, the iron core 2 is provided with thetwo protrusions 6. Alternatively, the number of the protrusion 6 can be,for example, four, six and eight. The plural protrusions 6 are favorablyplaced to be equally spaced from each other at the outer circumferenceof the iron core 2. The protrusions 6 extend outwardly in a radialdirection from a body portion of the iron core 2 and extend along therotary axis X. The longer a length L of the protrusion 6 in an axialdirection of the rotary axis X shown in FIG. 3, the greater the magneticforce can be generated. Resistance against rotary motion of the ironcore 2 can be appropriately generated by setting the length L of theprotrusion 6 appropriately.

In a case where the iron core 2 including the plural protrusions 6rotates inside the ring magnet 3, resistance (torque) for holding arotary position (phase) of the iron core 2 is generated by the magneticforce. Hereinafter, resistance applied to the resistance generatingdevice 1 will be explained with reference to FIG. 5. As shown in FIG. 5,the iron core 2 rotates in a direction of an arrow indicating a rotarydirection R. In a case where a rotary angle α of the iron core 2 is atzero degree, a center portion of the protrusion 6 of the iron core 2 ispositioned at a boundary between the S pole and the N pole of the ringmagnet 3. In those circumstances, the iron core 2 is in a stable stateand has a characteristic to be held at this position, that is, thecenter portion of the protrusion 6. In a case where the iron core 2rotates in the rotary direction R because the back door 200 is openedand closed by motive power of the motor 110 or by manual operation, theprotrusions 6 moves toward the S pole and a returning force RF that hasa characteristic to return the iron core 2 to an opposite direction tothe rotary direction R by the magnet force is applied to the iron core2. In a case where the rotary angle α of the iron core 2 is at 22.5degrees, the returning force RF comes to be maximum. The rotary angle αin which the returning force RF is maximized is changed in accordancewith the length of the protrusion 6 in the circumferential direction.For example, in a case where the length of the protrusion 6 in thecircumferential direction is shortened, the returning force RF comes tobe the maximum at the rotary angle α which is smaller than 22.5 degrees.In a case where the length of the protrusion 6 in the circumferentialdirection is extended, the returning force RF comes to be the maximum atthe rotary angle α which is greater than 22.5 degrees.

In a case where the iron core 2 rotates further in the rotary directionR, the returning force RF decreases. In a case where the rotary angle αof the iron core 2 is at 45 degrees, the iron core 2 comes to be in ametastable state where the magnetic force is not applied to the ironcore 2. The rotary angle α in which the iron core 2 comes to be in themetastable state is changed in accordance with a length of the ringmagnet 3 having the S pole in the circumferential direction. Forexample, in a case where the length of the ring magnet 3 having the Spole in the circumferential direction is shortened, the iron core 2comes to be in the metastable state at the rotary angle α which issmaller than 45 degrees. In a case where the length of the ring magnet 3having the S pole in the circumferential direction is extended, the ironcore 2 comes to be in the metastable state at the rotary angle α whichis greater than 45 degrees. In a case where the iron core 2 rotatesfurther in the rotary direction R, an advanced force AF advancing theiron core 2 in the rotary direction R is applied to the iron core 2 bythe magnetic force. In a case where the rotary angle α of the iron core2 is at 67.5 degrees, the advancing force AF comes to be maximum. Therotary angle α in which the advancing force AF is maximized is changedin accordance with the length of the protrusion 6 in the circumferentialdirection and the length of the ring magnet 3 having the S pole in thecircumferential direction. For example, in a case where the length ofthe protrusion 6 in the circumferential direction is shortened, theadvancing force AF comes to be the maximum at the rotary angle α whichis larger than 67.5 degrees. In a case where the length of theprotrusion 6 in the circumferential direction is extended, the advancingforce AF comes to be the maximum at the rotary angle α which is smallerthan 67.5 degrees. On the other hand, in a case where the length of thering magnet 3 having the S pole in the circumferential direction isshortened, the advancing force AF comes to be the maximum at the rotaryangle α which is smaller than 67.5 degrees. In a case where the lengthof the ring magnet 3 having the S pole in the circumferential directionis extended, the advancing force AF comes to be the maximum at therotary angle α which is greater than 67.5 degrees. In a case where theiron core 2 rotates further in the rotary direction R, the advancingforce AF decreases. In a case where the rotary angle α of the iron core2 is at 90 degrees, the iron core 2 comes to be in a stable state andhas the characteristic to be held at this position, that is, the centerportion of the protrusion 6. As described above, the rotary angle α inwhich the iron core 2 comes to be in the stable state is changed inaccordance with the length of the protrusion 6 in the circumferentialdirection and the length of the ring magnet 3 having the S pole in thecircumferential direction.

In a case where the iron core 2 further rotates, the relationshipbetween each of the aforementioned rotary angles α from 0 to 90 degreesand powers applying to the iron core 2 will be repeated. Thus, strongresistance (holding power) by the magnetic force is applied to the ironcore 2 in a case where the iron core 2 rotates by each of 0, 90, 180 and270 degrees (or every 0, 90, 180, and 270 degrees of the rotary angle).Accordingly, resistance which is generated intermittently is applied tothe iron core 2 in a case where the iron core 2 rotates. Thus, the ironcore 2 moves intermittently (to perform a machine-like movement). Theresistance against the opening and closing motions of the back door 200is generated by the magnetic force occurring between the iron core 2 andthe ring magnet 3. The resistance includes the holding force for holdingthe back door 200 in the opened state.

The back door 200 may be held at any desirable positions by theplacement of the resistance generating device 1 between the reductiongear 112 and the threaded spindle 113 of the drive unit 100. Moreprecisely, the back door 200 can be held at a door angle which can bechanged gradually with the machine-like movement in a case where theback door 200 is opened and closed. The more the rotary speed of themotor 110 is reduced by the reduction gear 112, the more efficiently theresistance generating device 1 can generate resistance.

According to the first embodiment, the resistance generating device 1generating resistance against the rotary motion of the threaded spindle113 is employed by a simple construction in which the iron core 2 andthe ring magnet 3 are placed between the reduction gear 112 and thethreaded spindle 113. Because the iron core 2 and the ring magnet 3generate magnetic torque in the non-contact manner, the abrasion of theiron core 2 and the ring magnet 3 can be inhibited. Accordingly, theresistance generating device 1 performs stably without an influence ofthe change of the surface of the iron core 2 or the ring magnet 3. Thus,the frictional noise between the iron core 2 and the ring magnet 3 isnot generated. Further, the resistance generating device 1 can be formedwithout an elastic member, for example, a spring. Thus, the life of theresistance generating device 1 may be extended.

Because resistance (holding power) generated between the iron core 2 andthe ring magnet 3 increases and decreases repeatedly, resistance isleveled in a case where the motor 110 or the threaded spindle 113rotates at a relatively high speed. Accordingly, in a case where themotor 110 or the threaded spindle 113 rotates at equal to or larger thana predetermined rotary speed, resistance (holding power) is released ordecreases so that a releasing device for releasing resistance (holdingpower) generated between the iron core 2 and the ring magnet 3 does notneed to be provided in addition to the resistance generating device 1.

According to the embodiments, the resistance generating device 1 maygenerate large resistance against the opening and closing motions of theback door 200 with a simple configuration. Further, the resistancegenerating device 1 includes holding power for holding the back door 200in the opened state. Because holding power is generated at regularintervals, for example, at 90 degrees, an operator can experience afavorable operation feeling, that is, a tactile feeling in a case wherean operator manually opens the back door 200. In a case where the backdoor 200 is opened and closed at a high speed, torque increasing anddecreasing by the magnetic force is leveled so that the resistanceagainst the opening and closing operations of the back door 200 may bereleased or may decrease.

Because the ring magnet 3 which has strong magnetic force is nowrelatively inexpensive in accordance with the development of, forexample, a motor, the manufacturing cost of the resistance generatingdevice 1 can decrease. Because the iron core 2 rotates relative to thering magnet 3 in the non-contact manner inside the ring magnet 3, theabrasion of the iron core 2 and the ring magnet 3 does not occur,leading to the extension of the life of the resistance generating device1. Because the iron core 2 and the ring magnet 3 are coaxially androtatably disposed with each other, torque for holding the phase of theiron core 2 strongly may be generated. Because the magnetic force can belargely generated by the extension of the length L of the iron core 2and then length L of the ring magnet 3 in the axial direction of therotary axis X, the resistance generating device 1 may generate largerresistance (holding power).

A second embodiment of this disclosure will be explained. Forconvenience of description, the same components as those described inthe first embodiment are marked with the same reference numerals, anddescription of the components will not be repeated. A drive unit of thesecond embodiment includes the same construction of the drive unit ofthe first embodiment and will not be explained. The construction of aresistance generating device 11 of the second embodiment is differentfrom the construction of the resistance generating device 1 of the firstembodiment and will be explained.

The difference of the resistance generating device 11 of the secondembodiment from the resistance generating device 1 of the firstembodiment will be explained. The same construction of the resistancegenerating device 11 as the construction of the resistance generatingdevice 1 will not be explained. According to the resistance generatingdevice 1 of the first embodiment, the iron core 2 serving as thetransmission member transmitting the motive power of the motor 110 tothe threaded spindle 113 is made from the magnetic body. A transmissionmember 12 of the resistance generating device 11 of the secondembodiment includes a body 13 (i.e., serving as a holding portion) whichcorresponds to a non-magnetic body and plural magnetic bodies 14 whichare provided at an outer circumference of the body 13.

As shown in FIG. 6, the resistance generating device 11 includes therotatable transmission member 12 and the ring magnet 3 (the fixingmember) which surrounds the outer circumference of the transmissionmember 12 in the non-contact manner. The ring magnet 3 is held by theholder 7. The transmission member 12 includes the body 13 which isrotatable and the plural magnetic bodies 14 placed at an outercircumference of the body 13. According to the embodiment, the fourmagnetic bodies 14 are provided, however is not limited. The number ofthe magnetic bodies 14 is not limited and can be, for example, two, six,and eight. The magnetic body 14 includes a material which is attractedto a magnet (ferromagnetic body), for example, an iron. The magneticbody 14 per se favorably corresponds to a magnetic body that does nothave a magnetic pole of the S pole or the N pole.

The body 13 is made from the non-magnetic body. The non-magnetic bodycorresponds to, for example, resin, aluminum and steel use stainless orSUS. According to the second embodiment, the body 13 is formed in asubstantially cylindrical-shape, however, is not limited as long as thebody 13 holds the plural magnetic bodies 14. As shown in FIG. 7, amodified example of a resistance generating device 21 of the secondembodiment is provided with a transmission member 22 which includes abody 23 (serving as a holding portion) which is rotatable and the pluralmagnetic bodies 14 which are provided at an outer circumference of thebody 23. The plural magnetic bodies 14 serve as plural protrusions andare fixed to the body 23. Similarly to the iron core 2 of the firstembodiment, the transmission member 12, 22 includes the first connectionportion 4 at the first end portion 2 a and the second connection portion5 at the second end portion 2 b. The first connection portion 4 isconnected to the reduction gear 112. The second connection portion 5 isconnected to the threaded spindle 113. The first connection portion 4rotates in response to the motive power of the motor 110 via thereduction gear 112. The transmission member 12, 22 transmits the rotarymotion inputted to the first connection portion 4 to the threadedspindle 113. According to the modified example of the second embodiment,the first and second connection portions 4, 5 and the body 13, 23 of thetransmission member 12, 22 are integrally formed. Alternatively, thefirst and second connection portions 4, 5 can be individually formedfrom the body 13, 23 of the transmission member 12, 22.

In a case where the transmission member 12, 22 rotates inside the ringmagnet 3, resistance (torque) for holding the rotary position (phase) ofthe transmission member 12, 22 is generated by the magnetic force. Asshown in FIG. 8, each of generating principles of the returning force RFand of the advancing force AF corresponds to be the same as each of thegeneration principles of the returning force RF and of the advancingforce AF of the first embodiment and will not be explained. In FIG. 8,resistance (holding power) of the first embodiment is shown in a dottedline. The resistance generating device 11 of the second embodiment cangenerate greater resistance (holding power) than the resistancegenerating device 1 of the first embodiment.

A third embodiment of this disclosure will be explained. For convenienceof description, the same components as those described in the firstembodiment are marked with the same reference numerals, and descriptionof the components will not be repeated. A drive unit of the thirdembodiment includes the same construction of the drive unit of the firstembodiment and will not be explained. The construction of a resistancegenerating device 31 of the third embodiment is different from theconstruction of the resistance generating device 1 of the embodiment andwill be explained.

The difference of the resistance generating device 31 of the thirdembodiment from the resistance generating device 1 of the firstembodiment will be explained. The same construction of the resistancegenerating device 31 as the resistance generating device 1 will not beexplained. According to the resistance generating devices 1, 11 of thefirst and second embodiments, each of the transmission members 2, 12includes a magnetic body and each of the fixing members 3 includes amagnet. Alternatively, a transmission member 32 of the resistancegenerating device 31 of the third embodiment includes a magnet and afixing member 33 (i.e., serving as a magnetic body) includes themagnetic body.

As shown in FIG. 9, the resistance generating device 31 includes thetransmission member 32 which is rotatable and the fixing member 33 whichsurrounds the outer circumference of the transmission member 32 in thenon-contact manner relative to the transmission member 32. Thetransmission member 32 includes a ring magnet 34 (i.e., serving as amagnet). An outer circumference of the ring magnet 34 includes pluralpoles. The fixing member 33 corresponds to a ring magnetic body. Thefixing member 33 includes plural protrusions 35 protruding toward thetransmission member 32 which is positioned inside the fixing member 33in the radial direction.

In a case where the transmission member 32 rotates inside the fixingmember 33, resistance (torque) for holding the rotary position (phase)of the transmission member 32 is generated by the magnet force. Thethird embodiment obtains the similar effects and advantages as theeffects and advantages of the first and second embodiments. In FIG. 9,the fixing member 33 of the resistance generating device 31 correspondsto the ring magnetic body. In FIG. 10, a resistance generating device 41of a modified example of the third embodiment includes the fixing member33 which is provided with plural magnetic bodies 43. The pluralseparated magnetic bodies 43 are held by the holder 7.

In a case where the transmission member 32 rotates inside the pluralmagnetic bodies 43, resistance (torque) for holding the rotary position(phase) of the transmission member 32 is generated by the magneticforce. The resistance generating device 41 of the modified example ofthe third embodiment obtains the similar effects and advantages as theeffects and advantages of the first and second embodiments.

A fourth embodiment of this disclosure will be explained. Forconvenience of description, the same components as those described inthe first embodiment are marked with the same reference numerals, anddescription of the components will not be repeated. A drive unit of thefourth embodiment includes the same construction of the drive unit ofthe first embodiment and will not be explained. The construction of aresistance generating device 41 of the fourth embodiment is differentfrom the construction of the resistance generating device 1 of the firstembodiment and will be explained.

According to the fourth embodiment shown in FIGS. 11 and 12, atransmission member 52 of a resistance generating device 51 is formedwith plural members in the axial direction of the rotary axis X. Each ofthe plural transmission members 52 is constructed to be displaced fromeach other in the rotary direction R by the rotation of the pluraltransmission members 52. Each of the plural transmission members 52 isdisplaced from each other in the rotary direction R so that resistancegenerated by the magnetic force may be reduced. Thus, resistancegenerated by the resistance generating device 51 can be reduced in acase where the motor 11 is activated.

As shown in FIG. 12, according to the resistance generating device 51 ofthe fourth embodiment, the transmission member 52 transmitting themotive power of the motor 110 to the threaded spindle 113 are formedwith two members. Alternatively, for example, the transmission member 52may be formed with three or four members which are more than three. Thetransmission member 52 is provided with a first transmission member 53and a second transmission member 54. Plural magnetic bodies 55 are fixedto an outer circumference of the first transmission member 53. Theplural magnetic bodies 55 are favorably placed to be equally spaced fromeach other at the outer circumference of the first transmission member53. Plural magnetic bodies 56 are fixed to an outer circumference of thesecond transmission member 54. The plural magnetic bodies 56 arefavorably placed to be equally spaced from each other at the outercircumference of the second transmission member 54, Each number of themagnetic bodies 55, 56 is not limited to four. Alternatively, eachnumber of the magnetic bodies 55, 56 can be, for example, two, six andeight.

The transmission member 52 is favorably made from a magnetic body. Asshown in FIG. 11, the first and second transmission members 53, 54 arerotatably supported with each other by a cylindrical shaft 57. As shownin FIGS. 13, 14, the first and second transmission members 53, 54 aresupported by the cylindrical shaft 57 so that a facing surface 58 of thefirst transmission member 53 face a facing surface 59 of the secondtransmission member 54.

For example, two compression springs 60 (i.e., serving as a biasingmember), elastic members, are placed between the first and secondtransmission members 53, 54. The facing surface 58 of the firsttransmission member 53 is provided with spring holding portions 61holding the compression springs 60, respectively. The facing surface 59of the second transmission member 54 is provided with spring holdingportions 62 holding the compression springs 60, respectively. Thecompression springs 60 are held between the spring holding portions 61,62 of the first and second transmission members 53, 54. The compressionsprings 60 facilitate the relative rotation of the first and secondtransmission members 53, 54 while generating resistance against therelative rotation of the first and second transmission members 53, 54.

As shown in FIG. 13, stopper portions 65 serving as stoppers areprovided at the facing surface 58 of the first transmission 53. As shownin FIG. 14, stopper portions 66 serving as stoppers are provided at thefacing surface 59 of the second transmission 54. In a case where thefirst and second transmission members 53, 54 relatively rotate with eachother, the stopper portions 65, 66 come in contact with each other toset relative rotation amounts of the first and second transmissionmembers 53, 54 within predetermined ranges.

The cylindrical shaft 57, the compression springs 60, and the stopperportions 65, 66 construct a means (portion) for changing a relativeposition of (or a position changing means (portion) for the relativeposition of) the first and second transmission members 53, 54 in therotary direction R. As shown in FIG. 11, the first transmission member53 includes a first shaft 63. The second transmission member 54 includesa second shaft 64. The first shaft 63 of the first transmission member53 is rotatably supported by one of the bearings 8 supported by theholder 7. The second shaft 64 of the second transmission member 54 isrotatably supported by the other of the bearings 8 supported by theholder cap 9. Accordingly, the first and second transmission members 53,54 rotate about the rotary axis X shown in FIG. 12.

As shown in FIG. 11, the transmission member 52 (the first and secondtransmission members 53, 54) is contained inside the ring magnet 3 (thefixing member). The ring magnet 3 surrounds an outer circumference ofthe transmission member 52 in the non-contact manner. The firstconnection portion 4 is connected to the first shaft 63 of the firsttransmission member 53. The second connection portion 5 is connected tothe second shaft 64 of the second transmission member 54. The firstconnection portion 4 is connected to the reduction gear 112. The secondconnection portion 5 is connected to the threaded spindle 113. The firstconnection portion 4 rotates in response to motive power of the motor110 via the reduction gear 112. The transmission member 52 transmits therotary motion inputted to the first connection portion 4 to the threadedspindle 113.

As shown in FIG. 15A, in a case where the motor 110 is in a stoppedstate, the first and second transmission members 53, 54 are in aninitial state where the magnetic bodies 55 of the first transmissionmember 53 and the magnetic bodies 56 of the second transmission member54 are placed at the same position in the rotary direction R, or placedto be overlapped with each other in the rotary direction R by biasingforce of the two compression springs 60. In a case where the first andsecond transmission members 53, 54 are in the initial state, themagnetic bodies 55 of the first transmission member 53 are aligned inlines with the magnetic bodies 56 of the second transmission member 54along the rotary axis X as shown in FIG. 12. Thus, the resistanceagainst the rotary motion of the threaded spindle 113 is generated bythe magnetic force occurring between the set of the magnetic bodies 55,56 of the first and second transmission members 53, 54 and the ringmagnet 3, Accordingly, in a case where an outer load, for example windand snow, is applied to the opened back door 200 to rotate the threadedspindle 113, the magnetic bodies 55, 56 and the ring magnet 3 generatethe holding force for inhibiting the rotation of the threaded spindle113.

In a case where the motor 110 rotates, as shown in FIG. 15B, the firstand second transmission members 53, 54 relatively rotate with each otherby the compression of one of the compression springs 60 and theextension of the other of the compression springs 60. The first andsecond transmission members 53, 54 are in a displaced state where themagnetic bodies 55 of the first transmission member 53 and the magneticbodies 56 of the second transmission member 54 are displaced from eachother in the rotary direction R. In those circumstances, the stopperportion 65 of the first transmission member 53 comes in contact with thestopper portions 66 of the second transmission member 54 to inhibit therelative rotation of the first and second transmission members 53, 54 bya predetermined rotary amount or higher. This holding is performed inorder to inhibit the damage of the compression springs 60 as well asestablishing a state where the magnetic bodies 55 (56) are placed to beequally spaced from each other in the whole circumference to minimizethe resistance holding force.

As shown in FIG. 16, in a case where the first and second transmissionmembers 53, 54 are in the displaced state, the position (phase) of themagnetic bodies 55 of the first transmission member 53 and the position(phase) of the magnetic bodies 56 of the second transmission member 54are displaced from each other when seen along the rotary axis X. Thatis, the position (phase) of the magnetic bodies 55 of the firsttransmission member 53 and the position (phase) of the magnetic bodies56 of the second transmission member 54 are displaced from each other inthe circumferential direction. Thus, the magnetic force generatedbetween the magnetic body 55 of the first transmission member 53 and thering magnet 3 and the magnet force generated between the magnetic body56 of the second transmission member 54 and the ring magnet 3 offset orbalance with each other and resistance against the rotary motion of thetransmission member 52 (the holding force of the transmission member 52)is released (decreased). Accordingly, torque is inhibited fromincreasing in a case where the motor 110 is activated.

According to the fourth embodiment, the transmission member 52 includesthe magnet bodies 55, 56. The ring magnet 3 is placed at the outercircumference of the transmission member 52. Alternatively, thetransmission member 52 can include a magnet and a fixing member placedat the outer circumference of the transmission member 52 can include amagnetic body. According to the embodiments, the rotary body correspondsto the threaded spindle 113, Alternatively, the rotary body can be aconnection device or a gear.

According to the embodiments, the first connection portion 4 (powerreceiving portion) receives the motive power of the motor 110, howeveris not limited. The first connection portion 4 (power receiving portion)can be constructed to receive the human power (power) of an operator.According to the aforementioned embodiments, the resistance generatingdevice 1, 11, 21, 31, 41, 51 is mounted to the drive unit for openingand closing the back door 200. Alternatively, a resistance generatingmechanism of this disclosure may be mounted to a motive powertransmission portion of a motor drive unit, for example, drive units fora power slide door and for a swing door, and may be mounted to a motivepower transmission portion of a hand operating system, for example, amanual seat lifting device and a wind regulator. The resistancegenerating device 1, 11, 21, 31, 41, 51 can generate resistance forinhibiting an opened door, a closed window or a lifted seat fromclosing, opening or falling due to the action of gravity.

According to the aforementioned embodiment, the resistance generatingdevice 1, 11, 21, 31, 41, 51 for the drive unit 100 opening and closingthe opening and closing member 200 of the vehicle 150 includes therotary body (the threaded spindle 113) being rotated for opening andclosing the opening and closing member (the back door 200), thetransmission member (the iron core 2, the transmission member 12, thetransmission member 22, the transmission member 32, the transmissionmember 52, the fits transmission member 53, the second transmissionmember 54) being rotated in response to the applied power, thetransmission member (the iron core 2, the transmission member 12, thetransmission member 22, the transmission member 32, the transmissionmember 52, the fits transmission member 53, the second transmissionmember 54) transmitting the rotary motion to the rotary body (thethreaded spindle 113), and the fixing member (3, 33) provided to formthe clearance between the fixing member (the ring magnet 3, the fixingmember 33) and the transmission member (the iron core 2, thetransmission member 12, the transmission member 22, the transmissionmember 32, the transmission member 52, the fits transmission member 53,the second transmission member 54) in the radial direction of the rotaryaxis X of the transmission member (the iron core 2, the transmissionmember 12, the transmission member 22, the transmission member 32, thetransmission member 52, the fits transmission member 53, the secondtransmission member 54), the fixing member (the ring magnet 3, thefixing member 33) surrounding the periphery of the transmission member(the iron core 2, the transmission member 12, the transmission member22, the transmission member 32, the transmission member 52, the fitstransmission member 53, the second transmission member 54). One of thefixing member (the ring magnet 3, the fixing member 33) and thetransmission member (the iron core 2, the transmission member 12, thetransmission member 22, the transmission member 32, the transmissionmember 52, the fits transmission member 53, the second transmissionmember 54) includes the magnet (3, 34) and the other of the fixingmember (the ring magnet 3, the fixing member 33) and the transmissionmember (the iron core 2, the transmission member 12, the transmissionmember 22, the transmission member 32, the transmission member 52, thefits transmission member 53, the second transmission member 54) includesthe magnetic body (the iron core 2, the protrusion 6, the magnetic body14, the fixing member 33, the magnetic body 43, the magnetic body 55,the magnetic body 56). The magnet (the ring magnet 3, 34) is disposed toface the magnetic body (2, 6, 14, 33, 43, 55, 56) so that the facingposition of the magnet (the ring magnet 3, 34) and the magnetic body(the iron core 2, the protrusion 6, the magnetic body 14, the fixingmember 33, the magnetic body 43, the magnetic body 55, the magnetic body56) facing each other is changed as the transmission member (the ironcore 2, the transmission member 12, the transmission member 22, thetransmission member 32, the transmission member 52, the fitstransmission member 53, the second transmission member 54) rotates. Themagnet (3, 34) is disposed to face the magnetic body (the iron core 2,the protrusion 6, the magnetic body 14, the fixing member 33, themagnetic body 43, the magnetic body 55, the magnetic body 56) so thatthe magnetic poles at the facing position of the magnet (the ring magnet3, 34) and the magnetic body (the iron core 2, the protrusion 6, themagnetic body 14, the fixing member 33, the magnetic body 43, themagnetic body 55, the magnetic body 56) alternate as the transmissionmember the iron core 2, the transmission member 12, the transmissionmember 22, the transmission member 32, the transmission member 52, thefits transmission member 53, the second transmission member 54) rotates.The magnetic body (the iron core 2, the protrusion 6, the magnetic body14, the fixing member 33, the magnetic body 43, the magnetic body 55,the magnetic body 56) and the magnet (the ring magnet 3, 34) generatethe magnetic force therebetween, the magnetic force generating theresistance against the opening and closing movement of the opening andclosing member (the back door 200).

According to the aforementioned embodiment, the resistance against theopening and closing motion of the back door 200 can be generated andreleased between the transmission member (the iron core 2, thetransmission member 12, the transmission member 22, the transmissionmember 32, the transmission member 52, the fits transmission member 53,the second transmission member 54) and the fixing member (the ringmagnet 3, the fixing member 33) in the non-contact state while reducingthe number of the magnet.

According to the aforementioned embodiment, the transmission member (theiron core 2, the transmission member 12, the transmission member 22, thetransmission member 32, the transmission member 52, the fitstransmission member 53, the second transmission member 54) includes theplural magnetic body portions (the protrusion 6, the magnetic body 14,the magnetic body 43, the magnetic body 55, the magnetic body 56)disposed at the outer peripheral portion of the transmission member (theiron core 2, the transmission member 12, the transmission member 22, thetransmission member 32, the transmission member 52, the fitstransmission member 53, the second transmission member 54), the pluralmagnetic body portions (the protrusion 6, the magnetic body 14, themagnetic body 43, the magnetic body 55, the magnetic body 56) extendingin the circumferential direction of the transmission member (the ironcore 2, the transmission member 12, the transmission member 22, thetransmission member 32, the transmission member 52, the fitstransmission member 53, the second transmission member 54).

According to the aforementioned embodiment, the resistance against theopening and closing motion of the back door 200 can be generated andreleased between the transmission member (the iron core 2, thetransmission member 12, the transmission member 22, the transmissionmember 32, the transmission member 52, the fits transmission member 53,the second transmission member 54) and the fixing member (the ringmagnet 3, the fixing member 33) in the non-contact state while reducingthe number of the magnet.

According to the aforementioned embodiment, the transmission member (12,22) includes the holding portion (the body 13, the body 23) which is thenon-magnetic body, the holding portion (the body 13, the body 23)holding the plural magnetic body portions (the magnetic body 14).

According to the aforementioned embodiment, the plural magnetic bodies14 can be held by the body 13, 23.

According to the aforementioned embodiment, the fixing member (the ringmagnet 3) is formed in the ring shape. The fixing member (the ringmagnet 3) is the ring magnet (3) of which magnetic poles alternate inthe circumferential direction of the ring magnet (3).

According to the aforementioned embodiment, the resistance against theopening and closing motion of the back door 200 can be generated andreleased between the transmission member (the iron core 2, thetransmission member 12, the transmission member 22, the transmissionmember 32, the transmission member 52, the fits transmission member 53,the second transmission member 54) and the fixing member (the ringmagnet 3, the fixing member 33) in the non-contact state while reducingthe number of the magnet.

According to the aforementioned embodiment, the opening and closingmember (the back door 200) is the back door (200) of the vehicle (150)and the rotary body (the threaded spindle 113) is the threaded spindle113 for opening and closing the back door (200).

According to the aforementioned embodiment, the resistance against theopening and closing motion of the back door 200 can be generated andreleased between the transmission member (the iron core 2, thetransmission member 12, the transmission member 22, the transmissionmember 32, the transmission member 52, the fits transmission member 53,the second transmission member 54) and the fixing member (the ringmagnet 3, the fixing member 33) in the non-contact state while reducingthe number of the magnet.

According to the aforementioned embodiment, the transmission member (theiron core 2, the transmission member 12, the transmission member 22, thetransmission member 32, the transmission member 52, the fitstransmission member 53, the second transmission member 54) is connectedto the reduction gear (112) and receives the drive force of the motor(110) via the reduction gear (112).

According to the aforementioned embodiment, the more the rotary speed ofthe motor 110 is reduced by the reduction gear 112, the more efficientlythe resistance generating device 1 can generate resistance.

According to the aforementioned embodiment, the transmission member (thetransmission member 52, the first transmission member 53, the secondtransmission member 54) includes the first transmission member (53) andthe second transmission member (54) separately provided from each otherand disposed in an axial direction of the rotary axis (X) of thetransmission member (the transmission member 52, the first transmissionmember 53, the second transmission member 54). The magnetic body portion(55) provided at the first transmission member (53) is displaced fromthe magnetic body portion (56) provided at the second transmissionmember (54) in the rotary direction (R) of the transmission member (thetransmission member 52, the first transmission member 53, the secondtransmission member 54) during the rotation of the transmission member(the transmission member 52, the first transmission member 53, thesecond transmission member 54).

According to the aforementioned embodiment, each of the pluraltransmission members 52 is displaced from each other in the rotarydirection R so that resistance generated by the magnetic force may bereduced.

The principles, preferred embodiment and mode of operation of thepresent invention have been described in the foregoing specification.However, the invention which is intended to be protected is not to beconstrued as limited to the particular embodiments disclosed. Further,the embodiments described herein are to be regarded as illustrativerather than restrictive. Variations and changes may be made by others,and equivalents employed, without departing from the spirit of thepresent invention. Accordingly, it is expressly intended that all suchvariations, changes and equivalents which fall within the spirit andscope of the present invention as defined in the claims, be embracedthereby.

The invention claimed is:
 1. A resistance generating device for a driveunit opening and closing an opening and closing member of a vehicle,comprising: a rotary body being rotated for opening and closing theopening and closing member; a transmission member being rotated inresponse to an applied power, the transmission member transmitting arotary motion to the rotary body; and a fixing member provided to form aclearance between the fixing member and the transmission member in aradial direction of a rotary axis of the transmission member, the fixingmember surrounding a periphery of the transmission member; wherein oneof the fixing member and the transmission member includes a magnet andthe other of the fixing member and the transmission member includes amagnetic body; the magnet is disposed to face the magnetic body so thata facing position of the magnet and the magnetic body facing each otheris changed as the transmission member rotates; the magnet is disposed toface the magnetic body so that magnetic poles at the facing position ofthe magnet and the magnetic body alternate as the transmission memberrotates; the magnetic body and the magnet generate a magnetic forcetherebetween, the magnetic force generating a resistance against anopening and closing movement of the opening and closing member; and thetransmission member is connected to a reduction gear and receives adrive force of a motor via the reduction gear.
 2. The resistancegenerating device according to claim 1, wherein the transmission memberincludes a plurality of magnetic body portions disposed at an outerperipheral portion of the transmission member, the plurality of magneticbody portions extending in a circumferential direction of thetransmission member.
 3. The resistance generating device according toclaim 2, wherein the transmission member includes a holding portionwhich is a non-magnetic body, the holding portion holding the pluralityof magnetic body portions.
 4. The resistance generating device accordingto claim 1, wherein the fixing member is formed in a ring shape, thefixing member is a ring magnet of which magnetic poles alternate in acircumferential direction of the ring magnet.
 5. The resistancegenerating device according to claim 1, wherein the opening and closingmember is a back door of the vehicle and the rotary body is a threadedspindle for opening and closing the back door.
 6. A resistancegenerating device for a drive unit opening and closing an opening andclosing member of a vehicle, comprising: a rotary body being rotated foropening and closing the opening and closing member; a transmissionmember being rotated in response to an applied power, the transmissionmember transmitting a rotary motion to the rotary body; and a fixingmember provided to form a clearance between the fixing member and thetransmission member in a radial direction of a rotary axis of thetransmission member, the fixing member surrounding a periphery of thetransmission member; wherein one of the fixing member and thetransmission member includes a magnet and the other of the fixing memberand the transmission member includes a magnetic body; the magnet isdisposed to face the magnetic body so that a facing position of themagnet and the magnetic body facing each other is changed as thetransmission member rotates; the magnet is disposed to face the magneticbody so that magnetic poles at the facing position of the magnet and themagnetic body alternate as the transmission member rotates; the magneticbody and the magnet generate a magnetic force therebetween, the magneticforce generating a resistance against an opening and closing movement ofthe opening and closing member; the transmission member includes aplurality of magnetic body portions disposed at an outer peripheralportion of the transmission member, the plurality of magnetic bodyportions extending in a circumferential direction of the transmissionmember; the transmission member includes a first transmission member anda second transmission member separately provided from each other anddisposed in an axial direction of the rotary axis of the transmissionmember; and the magnetic body portion provided at the first transmissionmember is displaced from the magnetic body portion provided at thesecond transmission member in a rotary direction of the transmissionmember during a rotation of the transmission member.